After all, services like Facebook Places and Foursquare make it easy to “check in” to places without actually going to them. And the premise of Yelp’s new incentive program is that deals should go to people who are frequenting local businesses already.It’s an issue that Foursquare confronted earlier this year, launching a feature that attempts to verify users’ location via GPS before granting them badges.

“We really wanted to do our due diligence to make sure we were doing as much as possible on (security),” spokeswoman Chantelle Karl said.

The company was reluctant to say too much about their security measures — “We don’t delve too much into the secret sauce,” Karl said — but she did offer a couple hints about the company’s approach.

Like Foursquare, Yelp tries to reconcile your phone’s GPS location with the business you’re checking in to. Yelp also looks at your user history — checking in to dozens of establishments in a single day is likely to raise an alarm.

The system is also smart enough to know what hours a business is supposed to be open, so checking in to a brunch spot at midnight will draw suspicion.

Raise too many alarms, and Yelp will block your check-in privileges.

“If we deem that person to not be trustworthy, they won’t be able to check in,” Karl said.

And even if some fake check-ins slip through, she said, cashing in an offer still requires a person to patronize a business.

“The beauty of it is that to take advantage of the check-in you actually have to be there,” Karl said.